International Publication No. 2006/000631 and U.S. Pat. No. 6,323,811 each disclose an antenna device having a structure in which open ends of two radiating elements are placed close to each other and power is fed to one of the radiating elements.
Japanese Unexamined Patent Application Publication No. 2004-363848 discloses an antenna device in which one parasitic element for shared use is added to two antennas operated at the same frequency.
Japanese Unexamined Patent Application Publication No. 2005-86780 discloses an antenna device in which, in different applications for the same frequency, each of their null directions is directed to each other's antenna element by adding L-shaped parasitic elements to the corresponding corners of a substrate.
For example, antennas used in wireless fidelity (Wi-Fi), are required to have gain in two frequency bands, a 2.4 GHz band and a 5 GHz band. Electronic apparatuses, such as TVs and DVD and BD players, may include a Wi-Fi antenna that uses a multiple input multiple output (MIMO) system. There is often a wall behind such an electronic apparatus, and access points are often located forward of the electronic apparatus. Given such conditions of use of the electronic apparatus, the intensity of radio waves from the rear of the electronic apparatus may be lower than that of radio waves from the front of the electronic apparatus. This means that directivity with gain higher at the front than at the rear is required.